The present invention relates to chair controls or tilt mechanisms and more particularly to a chair including provision for synchronizing the tilting of a seat and a back.
Various forms of tilt mechanisms for office chairs and the like have heretofore been proposed. Generally, such mechanisms permit the chair to tilt or recline rearwardly with respect to a base or support pedestal. In one form, a separate back tilts with respect to a base while the seat portion remains in a fixed position. In another form, the seat and back are formed as an integral or rigidly connected unit. The seat and back tilt together in unison through the same arc with the forward portion of the seat being raised. In other forms of chairs, the seat and back are separate members. They are interconnected, however, so that their tiling action is synchronized with the back tilting through an angle greater than that of the seat. Examples of prior tilting mechanisms may be found in commonly owned U.S. Pat. No. 4,776,633, entitled INTEGRATED CHAIR AND CONTROL and issued on Oct. 11, 1988 to Knoblock et al; U.S. Pat. No. 4,494,795, entitled VARIABLE BACK ADJUSTER FOR CHAIRS and issued on Jan. 22, 1985 to Roossein et al; U.S. Pat. No. 4,479,679, entitled BODY WEIGHT CHAIR CONTROL and issued on Oct. 30, 1984 to Fries et al; and U.S. Pat. No. 4,438,898 entitled CHAIR CONTROL LOCKING MECHANISM and issued on Mar. 27, 1984 to Knoblauch et al.
U.S. Pat. No. 4,575,150 entitled SUSPENSION ARRANGEMENT FOR A TILTING CHAIR and issued on Mar. 11, 1986 to Smith discloses a task chair having a tilt action between a seat and a back. A back support is pivotally attached by a helical coil spring to a stationary support or base. The seat is attached to the base by a forward pair of helical springs and to the back support by a rearward pair of helical springs. Pivot pins or pivot supports are omitted and the back and seat are interconnected to each other and the base solely by springs.
With prior tilt mechanisms, as the chair is reclined, pressure is applied &:o the underside of the user's thighs. The forward lip of the chair is raised, thereby lifting the user's legs. This lifting action can result in muscular discomfort and circulation problems. On approach to eliminating leg lift is disclosed in commonly owned U.S. Pat. No. 4,498,702, entitled SEATING UNIT WITH FRONT FLEX AREA and issued on Feb. 12, 1985 to Raftery et al. As disclosed therein, the chair includes a forward lip or thigh support area which is attached to the seat by leaf springs. When the chair is tilted, the articulated seat forward area will flex downwardly to limit leg lift.
A need exists for a unique synchronized chair tilting or control mechanism which will eliminate leg lift, reduce compression of the thighs and automatically adjust to the anatomical requirements of the user.